1. Field of the Invention
The present invention relates to an optical receiver module.
2. Description of the Related Art
In recent years, an optical receiver module having a transmission speed of about 10 Gbps is generally shaped into a coaxial package or a box package. A light receiving element and a transimpedance amplifier are proximally included in the package. Also, a lens is mounted on the package, and a light signal input through a fiber is converted into an electric signal through an absorption layer (light receiving portion) of the light receiving element by photoelectric conversion after a beam spot has been narrowed by the lens. The electric signal is as weak as about several microamperes to several milliamperes, and therefore amplified by the transimpedance amplifier, and output as a voltage signal.
Also, a bias to be applied to the light receiving element, and a power supply to be supplied to the transimpedance amplifier are arranged outside of the package. In a high-speed optical receiver module of 10 Gbps or more, in order to prevent generation of noise and signal deterioration caused by oscillation, the bias and a power line are designed to pass through an electrode pad such as a plate capacitor or a chip capacitor within the package.
An electric connection between an interior and an exterior of the package is conducted by a read pin attached to the package, or a transmission line pattern wired on a ceramic substrate. This optical receiver module is disclosed in JP 2003-134051 A, JP 2005-108935 A, and JP 2007-242708 A.
In general, it is desirable that in the optical receiver module, for example, a resonance causing malfunction is suppressed, and peaking and dipping are reduced to flatten the transmission characteristic as much as possible. In order to flatten the transmission characteristic as much as possible, for example, JP 2003-134051 A, JP 2005-108935 A, and JP 2007-242708 A disclose that a resistance thin film or a resistance element is inserted in series between lines for supplying a bias or signal lines which are patterned on a carrier (metallization substrate).